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10.5 Nonlocalities
The actualisation of propensities is an essentially non-local process.
This is because the initial extended field of propensity must act as
a whole in order to produce an actual event at a single place, and
the choice of one actualising, in order to `block off' all the
incompatible possibilities, must be immediately felt in all
regions of the potentiality distribution. This `unified action' occurs no
matter how widely spread the propensity field may be: it could, for
example, be the propensity field of a single photon spread out over many
light years in all spherical directions! I explained in chapter
8
how this need not necessarily violate the special theory of relativity.
Relativity only limits communications or law-like signals to the speed of
light -- it leaves open the possibility that the effects of purely
contingent orderings could be felt simultaneously over large spatial
regions.
Although in chapter
9
it was explained that propensities were the underlying `subject' or
`matter' of quantum objects, note that, because actualising does
not involve the motion of material, propensities are
not like `material' spread out. To understand this, we have to
change our ideas about matter and its localisation. Strictly speaking, we
have to say that a propensity distribution is not actually spread out in
space according to its field form, but rather its field distribution
describes where it can act in space and time. In an important
sense, therefore, propensity fields are non-local objects, at
least within the extensions of their own fields. The field distribution
behaves like a shadow of an object not in the space of the shadow. The
waves of the field distribution are not like waves in water: The wave's
oscillatory fluctuations at each point in such a material medium would be
only related by causal linking mechanisms, and cannot act as a whole apart
from the sequential actions of those mechanisms. An extended water wave
cannot, for example, become suddenly localised in a single place.
Physicists have come to realise increasingly that quantum mechanics is a
non-local theory, ever since the significance of the Bell's inequalities
has become apparent (see Clauser & Shimony [1978]). Redhead [1987] shows
how any realistic extension of quantum mechanics will therefore have to
use non-local properties and/or causal connections. He shows
that in the propensity interpretation of quantum mechanics, EPR processes
violate a `locality principle' which he puts
10.11
in the form
LOC1: An unsharp value for an observable cannot be changed
into a sharp value by measurements performed `at a distance'.
Physicists, however, have not always known how to deal with this fact,
largely because they have not had any paradigms to restrict non-local
models from completely arbitrariness. There are so many more possibilities
for interactions in non-local models compared with local models, that
physicists have tended to be bewildered by this new enormous range of
possibilities.
Smolin [1986] points out, for example, how the naive application of
equipartition in the thermodynamic limit of non-local theories would
result in the complete swamping of local interactions by all the many more
numerous non-local coupling terms. What we need therefore is a simple
paradigm for a nearly-local ontology, so we can begin to make small
departures from strict locality without getting lost in science-fiction
like realms of speculation. The theory of propensity fields is intended
to provide exactly this `minimal' non-locality.
Next: 11. Two Stages of
Up: 10. Quantum Substances
Previous: 10.4 Measuring as Actualising
Prof Ian Thompson
2003-02-25
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